1. Field of the Invention
The present invention relates to plug doors for railway cars and, in particular, to safety devices to prevent these doors from falling over and causing damage when they become derailed.
2. Description of the Prior Art
The prior art is generally cognizant of railway plug doors having safety rollers to help support the plug door when it is derailed. Such a safety roller is shown in U.S. Pat. No. 3,913,269. It has been a problem with such a roller that inasmuch as it is necessary to provide recesses in the retaining guide in which they must travel, there is no sure way to make sure that the safety roller cannot pass through one of these recesses to become freed from the retaining guide and thereby useless. Other prior art plug doors are shown in U.S. Pat. No. RE 27,029, No. 2,658,243, No. 2,765,502, No. 3,332,168 and No. 3,339,323.